The present invention relates to a portable information-processing apparatus such as a portable computer having a display unit, and more particularly to a display-unit housing which has a pointing stick, a click switch button, and the like.
Portable computers developed very recently have a housing and a display unit, both reduced in size to meet the demand made in the market. The smaller the housing, the smaller the component-mounting space available in the housing. It has therefore become difficult to arrange all of the required functional components within the housing.
In the case of a portable computer small enough to be put into a suit pocket, the keyboard occupies the entire upper surface of the housing. It is therefore impossible to arrange a pointing stick, a click switch button and the like on the upper surface of the housing. This is why a pointing stick, a click button and the like are mounted on the display unit.
The display unit is supported on the housing and can rotate between a first position and a second position. When rotated to the first position, the display unit covers the keyboard. When rotated to the second position, it exposes the keyboard. The display unit comprises a liquid crystal display (LCD) and a housing incorporating the LCD. The LCD has a screen for displaying characters, images and the like. The housing is made of synthetic resin and comprises a front wall and a rear wall. The front wall has an opening, through which the screen of the LCD is exposed. The rear wall opposes the front wall.
The pointing stick is arranged on the front wall, located near the opening thereof. The click switch button is mounted on the rear wall of the housing. That is, the pointing stick and the click switch button are positioned in back-to-back relationship. A user can therefore operate the pointing stick with the thumb and the click switch button with the forefinger or middle finger.
With the conventional portable computer, the pointing stick and the click switch (actuated when the click switch button is pushed) are supported by the same support plate. More precisely, the pointing switch and the click switch are mounted on the front and back of the support plate, respectively. The support plate is fastened by screws to the rear wall of the housing. The support plate receives a pressure every time the user pushes the click switch button and transmits the pressure to the housing.
The conventional portable computer is made so small and light that it is next to impossible to reduce its wall thickness further. As a consequence, the housing can hardly be sufficiently rigid. The housing may be twisted when the user pushes the click switch button. Twisting of the housing, if any, is transmitted to the support plate which supports the pointing stick. Here is a problem. The pointing stick is designed to detect the strain it exerts on the support plate when the user operates it with a finger tip, thereby to move a pointer to a desired position on the screen of the display unit. The pointing stick, which is mounted on the support plate, detects the twisting of the housing as a strain. Consequently, the pointer is inevitably moved on the screen though the pointing stick is not operated at all.
Usually, the user pushes the click switch button after operating the pointing stick. To push the click switch button with the forefinger or middle finger, the user touches the front wall with the thumb. That is, the user pinches the housing with the thumb and either the forefinger or the middle finger. When the housing is pinched, the front wall is deformed because it is thin. The deforming of the front wall is transmitted to the support plate. The pointing stick, which is mounted on the support plate, detects this deforming as a strain. Also in this case, the pointer is inevitably moved on the screen though the user does not operate the pointing stick at all.
To prevent such an undesired moving of the pointer, the support plate can be made thicker or have ribs to become rigid enough not to be influenced by twisting of the housing of deforming of the front wall. If the support plate is made thicker or provided with ribs, however, it must be a die-cast molding and more expensive, ultimately raising the manufacturing cost of the portable computer. If the support plate has ribs, the ribs will decrease the space provided in the housing to accommodate various components.
Namely, various problems arise because both the pointing stick and the click switch are mounted the support plate.